This invention relates to announcement systems and, more particularly, to such systems which provide flexible system control.
In the past, recorded announcements have been provided via stand-alone equipment containing stored voice messages that were connected to the switch via an analog line or trunk. The messages have been stored in analog form on magnetic media (such as a tape or magnetic drum) or, in one recent case, the analog message signal from the switch has been digitally encoded and stored in the announcement equipment. In all cases, control of the announcement equipment has been limited by the sophistication of the signalling that can be done via an analog line or trunk.
In the most limited case, the announcement equipment appears as a conventional telephone to the switch. Thus, when the switch is directed to connect a customer to an announcement, it "calls" the announcement equipment. The announcement equipment, in response to the incoming call from the switch, answers the call and plays the announcement. When attached to a trunk, the switch can signal the announcement equipment to start playing a message by using trunk signalling techniques, e.g., winking or flashing, or seizing, the trunk to notify the equipment when to start playing the announcement.
In the most sophisticated case, the equipment still appears like a conventional telephone but, when the equipment answers the call, it accepts multi-frequency (MF) signalling from the switch to control the announcement. In most cases, however, each separate announcement requires a separate piece of announcement equipment and a separate line, or trunk, to the switch. More advanced announcement equipment has been designed to store more than one announcement, but they still associate one storage area with each announcement, e.g., equipment with four announcements require four separate areas on a recording drum. Therefore, the announcement playback scenarios are limited in complexity to whatever capabilities the switch has for connecting a single fixed announcement to a call.
One problem with such systems is that they lack flexibility to handle complex situations. One such example is the situation where it is desired to change the message depending upon some external event, such as an overload at a call answering system. This same type of situation can occur, for example, when a calling party is placed in an answering queue and it is desired to give the party an accurate assessment of the waiting time. Under this condition, not only must the message change from time to time, even while the calling party remains connected, but a large number of announcements would have to be stored in an announcement circuit, each available to be played to the calling party over any line at any time. Under existing systems, even assuming that the announcement circuit would have enough memory capacity for a large number of messages, and enough line or trunk circuits to connect the announcement circuit to the system, it would remain impossible to change the message once a connection to a particular message is made.